The potential nemesis of the Reagan administration showed its face last week amid a series of disconnected events involving taxes, corporate mergers and the Central Intelligence Agency.

The president's Achilles' heel is a respect for private wealth so ingenuous as to promote inequities in public policy and sleaziness among government officials.

Glimmers of the danger are all that have surfaced so far. So, if the president asserts discipline and reverts to the true faith of conservatism, the whiff of trouble does not have to blight the good start that has been made in the administration's first six months.

The inauguration ceremonies, back in January, gave warning of the potential trouble. The ostentatious show of limousines and jewels and furs and haute couture advertise president's affinity for those who had made big money recently -- the masters of the quick deal.

Economic policy has subsequently been shaped to reflect their interests. The tax bill now going through Congress is notable for favors to the rich. In large part because of the president's own personal influence, estate and gift taxes are being reduced almost to nonthingness. The administration's bill favors an across-the-board reduction in income taxes that inevitably saves more money for those who have than for those who haven't.

Proposed reductions in government spending go the other way. While some cuts in subsidies to the rich have been proposed, the burden will fall on those who depend most on welfare, subsidized medical care, government housing and government jobs -- that is to say, those with low incomes.

Business activity has also been deeply affected by the administration's love affair with the haves. The big action now centers around a wave of mergers and proposed mergers. The main actors are energy companies. Texaco and Mobil, for instance, have each raised war chests of around $5 billion to buy Conoco, which is also the subject of rival takeover bids from Du Pont, a major chemical concern, and Seagrams, the big liquor distributor. The boldness of the oil companies shows that they no longer feel it necessry to poor-mouth in order to avoid taxes on swollen profits.

As to the consequences, many of the proposed mergers -- but especially to takeover of one big oil company by another -- would increase concentration in an industry not notable for competitive pricing. The ability of the big companies to borrow, moreover, shows the way monetary policy is working. Prime interest rates of around 20 percent discourage individual buyers of homes and cars. But the richest companies can afford to borrow. They drive the rates up even further in ways that make life harder for sectors of the economy -- notably autos, housing and local government -- that are sensitive to interest charges.

Insensitivity by officials works to make such inequities even more painful. Still, the Reagan administration, for all its moralistic talk, shows considerable capacity to shrug shoulders when it comes to the pressing of advantages by the powerful. The Justice Department has positively encouraged big companies to go beyond what were formerly considered antitrust limits. The Treasury has not raised an eyebrow to discourage flush companies from driving interest rates higher. And now comes the case of William Casey, the director of the Central-Intelligence Agency.

Mr. Casey is a shrewed lawyer and Wall Street operator who made a pile by the kind of wheeling and dealing the president admires. He was rewarded with the CIA job. He disregarded the advice of the intelligence professionals to take on as a deputy director another business operator, Max Hugel. The disclosure of some dubious operations has forced Hugel to resign. Casey himself is involved in some transactions not exactly favorable to the leader of an agency that already suffers from low morale and a bad reputation with Congress and other agencies.

Even taken altogether, these assorted breaches of fair play and good taste amount to a cloud no bigger than a man's hand. If allowed to grow and grow and grow, to be sure, the cloud could eclipse the sun. But the Reagan administration, as an avowedly conservative regime, should have corrective forces at its disposal.

True conservative doctrine favors as just social order, and questions chiefly government's ability to achieve that ideal. It does not license giving advantages to the rich and the powerful at the expense of the poor and the humble. So to baffle its nemesis, what the administration mainly needs is the will to cleanse itself of the commercial greed that has so often in the past besmirched conservatism in America.